In projection display devices such as projectors, trapezoidal distortion may occur in projected images as a result of the relative relationship between the projecting optical axis of the projection display device and the screen. Thus, the projection display device normally includes means for correcting trapezoidal distortions.
Furthermore, the projection display device may synthesize an OSD (On Screen Display) image with a projected image corrected for trapezoidal distortion to display the synthesized image. In this case, the OSD image may be misaligned with the projected image corrected for trapezoidal distortion and spread out of the screen.
A projection display device described in Patent Document 1 corresponds to a technique for enabling the OSD image to be displayed without being misaligned with the projected image corrected for trapezoidal distortion.
This projection display device acquires the coordinates (uncorrected coordinates) of a reference point on the projected image uncorrected for trapezoidal distortion and the coordinates (corrected coordinates) of the reference point on the projected image corrected for trapezoidal distortion. The projection display device moves the display range of the OSD image based on the difference between the uncorrected coordinates and the corrected coordinates.
The image distortion is corrected in such a manner that the image is reduced taking into account the area of screen. The invention described in Patent Document 1 only changes the position of the OSD image and not the size of the OSD image. Thus, the projection display device described in Patent Document 1 determines whether or not the OSD image is located within the moved display range. When the OSD image fails to be located within the moved display range, the projection display device deletes some of OSD menu items in accordance with pre-registered priorities before displaying the OSD image.
This enables the OSD image to be displayed without being misaligned with the projected image corrected for trapezoidal distortion.    Patent Document 1: JP2007-193204A